Visual display screen arrangement

ABSTRACT

A visual display screen ( 100 ′) such as an LCD screen is provided with a display area ( 30 ) for displaying an image. The display area ( 30 ) extends as far as an optically inactive region ( 60 ), containing device drivers, at the edge of the screen.  
     A cover plate assembly ( 40 ) overlays the display area ( 30 ). The cover plate assembly is laminar and an upper translucent plastics layer ( 520 ) thereof is planar over the display area ( 30 ) but is curved at the edge to provide a lens there. Thus, the image in the display area viewed through the cover plate assembly ( 40 ) appears to be shifted to the edge of the screen ( 100 ′) so that the optically inactive region ( 60 ) becomes invisible. Two screens can be abutted adjacent each other with no visible join using this technique. Compression of the image at the edge compensates for edge distortion by the lens. Repeating of the image either side of the join between two screens increases the viewing angle beyond which the join appears.

[0001] This invention relates to a visual display screen arrangement.

[0002] Many modern electrical or electronic devices contain a visualdisplay. For example, mobile telephones, porkable and particularlypalm-held digital computers each contain a (typically) backlit liquidcrystal display (LCD) screen. In each case, the desire to miniaturiseand thus increase the portability of such devices is balanced by theneed to ensure that the screen that imparts information to the user hasan adequate viewing area. In the field of mobile telephones, theemergence of technologies to view Internet pages has provided a furtherneed to increase screen size.

[0003] Although a screen can be provided which is physically larger thanthe device to which it belongs, such a screen is susceptible to damageand increases the overall size of the device. Furthermore, there arepractical difficulties in forming larger screens of height and width 45cm or greater, for example.

[0004] Another problem with devices employing electrical screens inparticular is that. the active display area (that is, the area overwhich text and images is displayed, usually via an array of pixels) isby necessity smaller than the overall area of the screen. Typically, thescreen has a glass cover plate and will also have an edge, which may ormay not form a Hart of the cover plate. The edge must be of finitewidth, in order to protect the screen and mechanically support the glasscover plate. In LCDs, an edge is in any event necessary to contain theliquid crystals. Usually, the transistors and other electroniccomponents necessary to drive the LCD are located adjacent the activedisplay area as well. This means that the edge of the display is visibleto a viewer of the screen.

[0005] A number of approaches have been taken to try and address theproblem of the visible edge or edges of screens and LCD screens inparticular. JP-A-090185046 (Casio Computer Co., Ltd.) shows a displaydevice having two display elements with refraction plates overlayingthem. A diffusion plate overlays the refraction prate. The refractionplate bends light rays from across the display elements so as apparentlyto close the gap between two adjacent plates so as to form a largedisplay from two smaller ones. The problem with this arrangement is thatthe display device becomes heavier and more complex through theinclusion of the refraction plates.

[0006] EP-A-0,279,913 (Matsushita Electric Industrial Co., Ltd.) showsan alternative approach. Here, a light guide is employed to guide therays from the LCD elements to he viewing surface. Since a light guide isemployed for each pixel, this arrangement would be expensive tomanufacture.

[0007] Finally, EP-A-0,559,070 shows an LCD panel where an attempt hasbeen made to reduce the gap itself. The LCD panels are bent by 90° atthe edges so as to bring the active area physically closer to the edge.Then, the edge seal and contacts extend downwards from the surface ofthe screen and do not contribute to the gap. Even then, the gap is onlyreduced (to perhaps 1-2 mm), and whilst this would potentially beadequate for large wall displays using adjoining screens, it would stillbe visible in smaller (e.g. hand holdable) screens. Moreover, themanufacture of the screens of EP-A-0,559,070 would be much moredifficult than with ‘standard’ LCDs.

[0008] It is an object of the present invention to address theseproblems wish the prior art. Specifically, it is an object of thepresent invention to maximize the viewing area of a visual displayparticularly, but not exclusively, for use with a relatively smallelectronic device.

[0009] According to a first aspect of the present invention, there isprovided a visual display screen arrangement for displaying an image,comprising: image display means having a display area; a translucentcover member arranged to cover the display area and having a first covermember edge, the display area having an edge extending towards but notas far as the said first cover member edge; characterised in that thecover member has: (a) a generally planar portion covering at least apart of the display area and being arranged to pass rays of lightsubstantially without bending such that the majority of the display areaas viewed externally of the arrangement and through the said generallyplanar portion, appears substantially undistorted; and (b) a refractingportion which includes the said first cover member edge, the saidrefracting portion being arranged to bend only those rays of lightemanating from at or adjacent to the edge of the display area, such thatthe said display area as viewed externally of the arrangement andthrough the said refracting portion, appears to extend substantially asfar as the edge of the cover member.

[0010] With devices containing known display screens such as liquidcrystal displays or cathode ray tubes, the active viewing area is bydefinition smaller than the width of the device itself. In the case ofliquid crystal displays, this is because edge seals are necessary tocontain the liquid crystals between the cover member and the body. Sidewalls are also often employed to increase mechanical protection. In thecase of cathode ray tubes, again side walls are necessary because thetube itself must be evacuated, and also because the range of sweep of anelectron beam across tine tube (in order to form an image) must be lessthan the width of the tube itself. Thus, when two or more such knowndisplays are placed adjacent to one another, a visible gap occurs. Withliquid crystal displays, this visible gap is (with commerciallyavailable technology) approximately 3 mm wide. Such a gap isunacceptable, particularly for mobile telephone screens, for example,which may only be one order of magnitude larger than this.

[0011] The present invention overcomes these problems. By causing onlylight at the edge of the arrangement to be bent, whilst allowingtransmission through the translucent cover member away from the edgewithout any significant- bending or distortion, the gap can beeffectively made to disappear without requiring separate lenses orcomplex modifications to the arrangement.

[0012] Such a technique is-particularly advantageous where the screenarrangement comprises two panels abutting one another. Here, the joinbetween the two panels can be made apparently almost to disappear if thelight is bent by each panel where it abuts the other, but only at thatlocation.

[0013] In a particularly preferred embodiment, the visual display screenarrangement is further arranged to generate a part of an image bothwithin the first display area and adjacent the first cover member edge,and also within the second display area and adjacent the edge of thesecond cover member.

[0014] This technique reduces the visibility of the gap when theobserver moves out of perfect alignment with the screen arrangement (forexample, by viewing the arrangement at an angle to the plane of thepanels)

[0015] It is preferable that the image, when displayed in the displayare, is compressed adjacent to the respective panel edge. There areseveral ways of doing this. In one preferred embodiment, the or eachdisplay area has a resolution and, specifically, a pixel resolutionadjacent the respective panel edge which is higher than the pixelresolution of the or each display area away from the respective paneledge. Alternatively, the image itself may be compressed electronicallywithout then needing to compress to pixels adjacent the respective paneledge. Compression is useful to allow compensation for the distortingeffect of light ray bending, through a lens arrangement, for example.

[0016] Preferably, the generally planar portion of the or each covermember is coterminous with that part of the display area having therelatively lower resolution, and wherein the or each refracting portionis coterminous with that part of the display area adjacent to therespective cover member edge having the said relatively higherresolution. In other words, the non-distorting part of the cover memberoverlays the relatively low resolution pixels, whereas the light bendingpart of the cover member overlays the relatively high resolution pixels.

[0017] In the preferred embodiment, the refracting portion of the oreach cover member is formed with the cover member edge shaped so as toform a lens, such as a convex lens, to bend the light passingtherethrough. Other techniques for bending the light, such as coatingthe panel edge with a high refractive index material, or incorporationof other materials, may also be used.

[0018] In preference, the cover member is formed as a laminarconstruction with, for example, a lower layer adjacent to the displayarea and formed of a first material, an upper layer formed of a second,different material, and a polarisation/compensation layer sandwichedbetween the upper and lower layers. In that case, the lower layer may beformed of glass and the upper layer of a plastics material. This allowsa very simple construction for the arrangement. A ‘standard’ LCD can bemade without any changes to the glass layer. A plastics layer can thenbe laminated on top, and its edge bevelled for example to provide thelight bending at that edge. Then the glass layer (which may containdelicate structures) need not be machined.

[0019] Not withstanding such preferred features, it is to be understoodthat, by cover member is meant any physical structure, or part of aphysical structure, which covers, surrounds or even provides a part ofthe display area of the image display means, such as the body or screenof a CRT, or the translucent panel and/or edge seal and/or other bodyparts of an electronic display such as an LCD. In particular, the covermember may contain active elements of the display.

[0020] According to a further aspect of the present invention, the e isprovided a visual display screen arrangement for an electronic devicecomprising a first screen member having a first active display area anda first joining edge, and a second screen member having a second activedisplay area and a second joining edge;

[0021] the first and second screen members being movable between a firstposition and a second position, in which second position the first andsecond joining edges are adjacent, the first and second screen membersare generally coplanar, and the first active display area appears to auser substantially to abut the second active display area at theconfluence of the first and second joining edges.

[0022] The arrangement of the present invention permits one large visualdisplay area to be provided through the collocation of two or moresmaller screen members. The active display areas of two or more screenmembers meet, or at least appear to meet, at a joining edge between thetwo or more screen members and, in the preferred embodiment, anelectronic device, with which the visual display screen arrangementcommunicates, addresses the two or more screen members separately sothat a single image (for example), scanning both or each screen member,may be displayed.

[0023] In the preferred embodiment, the arrangement further compriseshinge means connecting the first and second screen members andconstraining the first screen member and second screen member to befoldable between the first and second positions.

[0024] Such an arrangement is particularly advantageous for small,hand-held devices such as mobile telephones, video cameras or so-called“palm top” computers. When not in use, the overall height and width of adevice having the arrangement of the invention need be no larger thanpreviously. By unfolding the screen arrangement, however, a compositescreen which is much larger than the electronic device with which itcommunicates may be provided. The advantages of a mobile telephone witha composite screen which is, for example, 15-20 cm wide (rather than thestandard width of 3-5 cm) are manifest, particularly for telephones withInternet access.

[0025] Preferably, the screen members are each liquid crystal displays.The first and second screen members may each include a screen memberbody having a cover piece. Alternatively, a single cover piece may beshared by both screen members. Each cover piece or, alternatively, eachscreen member body then preferably forms a lens along the said first andsecond joining edges respectively and is arranged to shift the apparentlocation of the edge of the first and second active display areas sothat they appear to a user substantially to abut one another. With thisarrangement, even where the active display areas do not extend right tothe edge of the screen member (as will be the case with liquid crystaldisplays, for example), the lens arrangement bends light passing throughthe joining edges so that, as viewed from above the screen arrangement,the plurality of separate active display areas appears to a user as apseudo-continuous, single active display area.

[0026] In accordance with a third aspect of the present invention, thereis provided a visual display screen arrangement for displaying an image,comprising a panel and including a light bending region therein; andimage display means having a display area located beneath the panel, thedisplay area extending across a major portion of the panel area butcomprising at least one inactive zone in the display area, the or eachinactive zone being located substantially underneath the said lightbending region in the panel; wherein the light bending region isarranged to bend rays of light passing therethrough, such that an imageformed within the display area and viewed through the panel appears toextend across the inactive zone substantially without discontinuity.

[0027] The invention may be put into practice in a number of ways, andsome of these will now be described by way of example only and withreference to the following Figures in which:

[0028]FIG. 1 is a highly schematic sectional view through the edge oftwo prior art liquid crystal display (LCD) panels when placed adjacentone another;

[0029]FIG. 2 shows a highly schematic sectional view through the edge oftwo LCD panels, each having a display area and lens, placed adjacent oneanother, and embodying one aspect of the present invention;

[0030]FIG. 3 shows a sectional view through the edge of one of the LCDpanels of FIG. 2, in more detail;

[0031]FIG. 4 shows, in schematic plan view, the electronics employed todrive the two LCD panels of FIG. 2;

[0032]FIG. 5 shows suitable dimensions for the panel arrangement of FIG.3, based on calculations using Snell's law;

[0033]FIG. 6 shows the location of the LCD pixels in the view of FIG. 2including repeat pixels;

[0034]FIG. 7 shows a schematic plan view of the pixel arrangement in theapparatus of FIG. 2, indicating how the pixel spacing decreases towardsthe edge of the arrangement without the repeat pixels of FIG. 6;

[0035]FIG. 8a shows images formed in the display areas of each of thetwo LCDs of FIG. 2, without the lenses;

[0036]FIG. 8b shows suitable dimensions for a large scale model of theimage of FIG. 8a but with repeated strips;

[0037]FIG. 9 shows images formed in the display areas of each of the twoLCDs of FIG. 2 with the lenses, and as viewed from above;

[0038]FIGS. 10a and 10 b show ray diagrams for the panel arrangement ofFIG. 2, when viewed perpendicular to the plane of the panel and at anangle thereto respectively;

[0039]FIGS. 11a, 11 b and 11 c show alternative embodiments of oneaspect of the present invention;

[0040]FIG. 2 shows a visual display screen arrangement embodying afurther aspect of the present invention;

[0041]FIG. 13 shows a further embodiment of a visual display screenarrangement in accordance with the present invention; and

[0042]FIGS. 14a, 14 b, 14 c and 4 d show applications for the visualdisplay screen arrangements of FIGS. 2 to 13.

[0043] Referring first to FIG. 1, a highly schematic sectional viewthrough the edge of two prior art liquid crystal display panels 10, 10′is shown, roughly to scale. Each LCD panel comprises a supportingsubstrate 20 (typically including a reflector, first glass plate, firstpolarizing element and backlight where appropriate) onto which ismounted a glass cover plate 40. Sandwiched between the supportingsubstrate 20 and the glass cover plate 40 is a volume which forms anactive display region 30. The active display region 30 contains aplurality of electrodes, as will be familiar to those skilled in theart, together with liquid crystals.

[0044] The panels 10, 10′ may be bounded by side walls 1o 50 whichprovide mechanical protection to the panel. The liquid crystals arecontained within the active display region 30 also by an epoxy edge sealwhich typically has a protective layer thereon. In consequence of this,there is a region adjacent to the edge of the LCD panel which cannot beused. This optically inactive area 60 is, in present LCD panels,typically between 1 and 1.5 mm wide.

[0045] Because of the optically inactive area, 60, even if theprotective side walls 50 of two LCD panels 10, 10′ abut one another, aminimum total inactive region of around 3 mm in width is then present.

[0046] Thus, when placing two LCD panels adjacent to one another, avisible gap is clearly discernable between the two active displayregions. A significant “seam” is unacceptable and prior art arrangementsare accordingly unsuitable for creating larger screens from an array ofsmaller screens placed together.

[0047]FIG. 2 shows a highly schematic sectional view through-the edge oftwo LCD panels 100, 100′ embodying the present invention. Featurescommon to FIGS. 1 and 2 are labelled with like reference numerals.

[0048] In the arrangement of FIG. 2, instead of the flat, generallyplanar cover plate assembly 40 of FIG. 1, the cover plate assembly 140is instead curved at its edge, where it joins the protective side wall50. The curved edge 150 acts as a lens and refracts light as may be seenby the dotted lines in FIG. 2. This in turn has the effect of reducingthe apparent width of the visible gap. The radiused edge 150 is alsoless susceptible to damage.

[0049]FIGS. 3 and 5 show the edge geometry in more detail. Again,features common to FIGS. 1, 2, 3 and 5 are labelled with like referencenumerals. As seen in FIG. 3, the cover plate assembly 140 can benotionally divided into two separate regions, a generally planar region142 and a refracting region 144 which is convex in the example of FIG.3. The cover plate assembly 140 overlays a main display area 25 having adisplay region 30 which may be Liquid Crystal, Polymer, Bi-stable(I-ink(™) or the like. Within the display region is a plurality ofpixels 55 a, 55 b, 55 c, whose arrangement will be described in moredetail below. Light from the pixels 55 a, arranged away from theoptically inactive area 60, which includes the edge seal and edgeprotection, is substantially unaltered in direction by passage throughthe planar region 142 of the cover-plate assembly 140. This is shown inFIG. 3 by the rays 72. By contrast, light from pixels 55 b, for example,which are closer to the optically inactive area 60, is bent by therefracting region 144 of the cover plate assembly 140, as seen in rays74.

[0050]FIG. 3 also shows the supporting substrate 20 which may, forexample, be a sandwich of materials and elements necessary for display,such as a backlight 160, and in the same manner the cover plate assembly140 can be a sandwich of materials containing elements necessary for thedisplay.

[0051] The method of shaping the edge into a radius results in an imagethat appears at the edge. In order to compensate for the dimensionaldistortion resulting from the curved surface 150, the pixels arecompressed in regions B and C of the main display area 25 adjacent theoptically inactive area 60. Depending upon the shape of the refractingregion 144, the pixel resolution may be gradually increased or abruptlyincreased.

[0052] Region C is an image repetition zone. This is providedimmediately adjacent to the inactive region area 60. The purpose of thiswill be described in connection with FIGS. 10a and 10 b below. Theremainder of the main display area, A, contains the relatively lowerresolution pixels 55 a. It is to be understood that, in the preferredembodiment, the pixel spacing of the pixels 55 a may be the same as thespacing in a ‘normal’ LCD panel, with the pixels 55 b, 55 c being moreclosely packed. For ease of manufacture, however, it is instead possibleto use a display area 25 in which each separate pixel is equally spaced,and either to electronically compress the image, or, for example, toaddress two adjacent pixels in the region A in tandem, whilst addressingeach separate pixel in the regions B and C separately. In the latterarrangement, each pair of pixels in the region A acts as a single,larger pixel.

[0053] Using Snell's law, the geometry of the radiused edge 150 can beestimated. FIG. 5 shows the geometry in a “worst case” scenario, withglass, having a low refractive index, provided as part of the coverplate assembly 140. It is stressed here that the dimensions provided areby way of example only and that the dimensions are widely variabledependent upon the application and materials. It will be appreciatedthat the higher the refractive index, the thinner the cover plateassembly needs to be for a given width of optically inactive area 60.Using 0.7 mm thick glass (typical for LCDs), having a nominal refractiveindex of 1.5, and with the radiused edge 150 having a radius of 0.5 mm,the lateral distance over which the cover plate assembly 140 must becurved is 0.38 mm. The edge and seal width at the height of the liquidcrystal is over 220 μm, as opposed to 80 μm without edge shaping. For ascreen resolution of 75 dots per inch (30 dots per cm), only the pixelsimmediately adjacent to the optically inactive area 60 need to be ofcloser line spacing.

[0054]FIG. 4 shows, in schematic plan view, the electronics employed todrive the two TID panels of FIG. 2. Each panel is formed on a frame 200.Driver circuitry for addressing the transistors within the display isprovided on two sides of the screen only, rather than also at the joindefined by the protective side walls 50 of the two panels. It will, ofcourse, be understood that the driver circuits could instead be locatedbeneath the display.

[0055]FIG. 6 shows a further sectional view o: the arrangement of pixelswithin the active display region and it will again be noted that thepixel resolution increases with proximity to the optically inactive area60. The arrangement of FIG. 6 also includes so-called repeat pixelswhose purpose will be explained further in connection with FIGS. 10a and10 b. FIG. 7 shows, by contrast, a schematic plan view of the pixelarrangement in the arrangement embodying the invention, with horizontallines representing the rows of pixels. In FIG. 7, the repeat pixels ofFIG. 6 are not shown.

[0056]FIGS. 8a and 9 show an exemplary image formed in the activedisplay regions of each of the two LCDs of FIG. 2, without and then withthe lenses in place respectively. It will be noted from a comparison ofFIG. 8a and 9 that the image in the active display region is compressedas it approaches the inactive region, and that the lens compensates forthe visible gap and the compressed image such that the gap substantiallydisappears and the image as actually seen by a user is undistorted.

[0057] To verify the technique, an image such as is shown in FIG. 8a wasgenerated and printed onto white paper. Two perspex blocks, each havinga bevelled edge, were placed together so that the bevelled edgesabutted. The printed paper was backlit through a light box and thevisible gap shown in FIG. 8a reduced to the thin, almost invisible lineof FIG. 9.

[0058] The dimensions used were as follows: thickness of perspexblocks=9.2 mm; radius of curvature of edge=4.6 mm, subtending an arc of50°; refractive index of perspex=1.43. The image was formed with a 3.0mm black gap surrounded by 0.9 mm repeat strips (as explained below inconnection with FIGS. 10a and 10 b) and 2.2 mm compressed strips. Thisschematic image structure is shown in FIG. 8b.

[0059] The foregoing description has discussed refraction of light raysincident generally perpendicular to the planar part of the cover plateassembly 140, that is, when the screen is viewed face on. When anobserver moves out of perfect alignment to the screen, by contrast, thegap becomes more visible if certain precautions are not taken. This maybe explained with reference to FIGS. 10a and 10 b, which show a raydiagram for the cover plate assembly 140 of the panel arrangement ofFIG. 2 when viewed perpendicular to the plane of the panel and,separately, at an angle thereto respectively. Consider first the virtualpoint A in FIG. 10a. When viewed directly from above, this virtual pointis actually being displayed by a pixel at the location A′ within theactive display region 30. When the observer moves to the right, however,as shown in FIG. 10b, the virtual point a then falls behind the joindefined by the protective side walls 50 of each of the two LCD panels100, 100′. In order to overcome this, part of the image displayed in theactive display region 30 of the LCD panel 100 is repeated in the activedisplay region 30′ of the other LCD panel 100′. The virtual point A inFIG. 10b is now displayed by the pixel at location A″ in the right-handLCD panel 100′ instead. In other words, in the active display region 30′of the right-hand LCD panel 100′, the edge is projecting a section ofwhat is normally seen from the active display regain 30 of the left-handLCD panel 100.

[0060] By repeating the image on either side of the join where theprotective side walls 50 of the LCD panels 100, 100′ abut, theobserver's eye does not register the join even when viewing the screenaway from the perpendicular. Using such an arrangement, the angle ofviewing of the screen before the join becomes visible can be increasedfrom about 8° about an axis perpendicular to the display region 30, upto about 20° either side of that axis. The amount of repetition isvariable. For example, the test arrangement of FIG. 8b employs a 40%repetition, that is, the upper 40% of the image in the lower compressedstrip B is repeated in he upper repeat strip and vice versa. Increasingthe percentage gives better viewing angles but results in a narrowergap.

[0061] Referring now to FIGS. 11a to 11 c, different arrangements forrefracting the light around the inactive region of the LCD are shown. Inthe arrangement of FIG. 11a, two materials are employed, with a lowrefractive index material 220 formed over the radiused edge 150. Aspreviously explained, the higher the refractive index, the thinner thelens needs to be for a given width of inactive region.

[0062] To achieve a higher degree of refraction, two interfaces may beused as well or instead. For example, a region of low index ofrefraction material 230 may be employed adjacent to the supporting sidewall, as shown in FIG. 11b. In FIG. 11c, an undercut edge may beprovided to deflect the rays. The particular choice of shape will dependupon the maximum degree of reflection deemed permissible, amongst otherconsiderations. The region defined by the undercut edge of the coverplate assembly 140 may, for example, be filled with material such as aresin. In yet an alternative arrangement, the material could be situateddirectly on the active display, in an analogous manner to that shown inFIG. 11b. In general, to minimize the thickness of the cover plateassembly 140, it is desirable that the translucent part be formed of amaterial such as a relatively heavy flint glass having a refractiveindex in excess of 1.6. Other materials such as perspex or a lightweightglass coated plastics material could be employed instead, to save costs,but, having a lower refractive index, would need to be relativelythicker.

[0063]FIG. 12 shows a sectional view through an LCD screen arrangementembodying a further aspect of the invention. The arrangement of FIG. 12includes two separate panels having separate supporting substrates 20,two active display regions 30 containing liquid crystals or CRT pixelsand separated by an inactive area 60 and protective side walls 50, and acover plate assembly 140 formed of separate panel covers 45 but with asingle screen cover 47 covering both panels. In contrast to theembodiments of FIGS. 2-11, the arrangement is not intended to befoldable which is why a single screen cover 47 is instead provided tospan both of the active display regions 30. Two wedge shaped recesses250, 250′ are cut in the base of the screen cover 47 to act as lenseseither side of the join formed by the protective side walls 50. As withother embodiments, it is preferable that the part of the image formed atthe edge of one of the active display regions, adjacent the inactivearea 60, is repeated on the other side of the join, again in the regionimmediately adjacent to the inactive area 60. As with previousembodiments, the pixel spacing is reducing adjacent the inactive area60.

[0064] Even though the arrangement of FIG. 12 is not foldable, it isstill advantageous in that it allows a large composite screen to beformed from an array of smaller screens, with an essentially invisibleseam or seams. This is particularly advantageous for LCD, where thereare difficulties in manufacturing single, large area displays.

[0065] Turning now to FIG. 13, still a further embodiment of a visualdisplay screen arrangement is shown. For ease of explanation, only thecover plate assembly 140 notionally divided into a generally planarportion 142 and a refracting portion 144) is shown. It will beunderstood that a main display area and supporting substrate aretypically located below the cover plate assembly 140, however.

[0066] In contrast to the embodiment of, say, FIG. 5, the cover plateassembly 140 is Preferably made up of a stack of layers. A lower layer500, adjacent to the (not shown) main display area, is typically formedof glass. On top of that is a thin sandwich layer 510 ofpolarisation/compensation material. Finally, an upper layer 520 of atough plastics material is laid down on top of the thin sandwich layer510.

[0067] The glass lower layer 500 and the polarisation/compensationmaterial of the thin sandwich layer 510 are, as may be seen, of‘standard’ shape without any means to cause light to bend. Instead, itis the plastic upper layer 520 which contains the curved edge thatcauses light refraction.

[0068] There are a number of benefits to this arrangement. Firstly, theoverall weight of the cover plate assembly 140, and thus the visualdisplay screen as a whole, is reduced relative to a solid glass coverplate assembly. This is particularly desirable in lightweight devicessuch as PDAs or mobile telephones where a few grammes can be important.Secondly, the laminar construction of FIG. 13 allows any shaping at theedge of the cover plate assembly to take place on the plastic upperlayer 520, well away from any sensitive components in or near the glasslower layer 500. Finally, it reduces still further manufacturingcomplexity relative to the prior art. The top of traditional LCDsalready comprises a lamination of glass and polarisation/compensationmaterial forming a panel approximately 0.6 mm thick. Thus, a perspexsheet may simply be laid down on top of this, either before or afteredge shaping, to achieve the composite cover member of FIG. 13.

[0069] It is to be understood, of course, that a single glass sheetproviding the cover plate assembly also has its advantages, particularlyin terms of refractive index which makes the amount of curvaturerequired less.

[0070] Suitable dimensions for a device are set on FIG. 13 itself. Thesevalues are for guidance only and it will also be appreciated that thegeometrical arrangement provides for direct scaling of the values given.

[0071] Turning finally to FIGS. 14a-14 d, some exemplary applicationsfor the arrangements of FIGS. 2-13 are shown. FIG. 14a shows a firstmobile telephone 300 having a body part.305 with a keyboard, and ascreen formed from two LCD screen parts 310 and 320, each of which isgenerally of similar dimensions to the keyboard. The screen parts arefoldable relative to one another by means of a hinge (not shown) suchthat, in a first, closed, position, the cover plate assembly of onecontacts that of the other. This protects the screen parts 310, 320 whennot in use. in a second, open position as shown in FIG. 14a, the twoscreen parts are folded away from one another. By addressing each screenpart 310, 320 differently (which technique will be familiar to thoseskilled in the art), a composite image as seen in the Figure can then beforced and this extends across the join 325 to fill the whole screen.

[0072]FIG. 14b shows a second mobile telephone 330 with a foldablescreen containing three screen parts 340, 350, 360. The central screenpart 350 is mounted in fixed relation to the body of the mobiletelephone, and the left and right-hand parts 340, 360 are foldablerelative thereto. Thus, in a first position, the left-hand screen part340 folds against the central screen part 350 such that the cover plateassemblies thereof face one another. After that, the right-hand screenpart 360 is folded over the back of the left-hand screen part 340 sothat the cover plate assembly of the right-hand screen part 360 facesthe supporting substrate 2C of the left-hand screen part 340. Whenopened, the composite screen has three parts with two joins 370, 380.The principle of a three-part screen arrangement is exactly the same ashas been described with the one and two-part screen arrangements ofFIGS. 2 to 13. Obviously, the central screen part 350 requires shapededges on both sides. In that case, i. may be desirable to have thedriver circuits to address the central screen part 350 underneath thesupporting substrate, but this is not a problem since the central screenpart 350 is mounted upon the body of the telephone.

[0073]FIG. 14c shows a foldable touch screen device 390 which has atouch screen keyboard 400. This device is capable of lying flat upon atable when unfolded and is thus less intrusive than a laptop computer.The device 390 can also be used as an. electronic book and in that casethe virtual keyboard may be switched off. A disk drive 410 might also beprovided to allow information to be uploaded and downloaded.

[0074] Finally, FIG. 14d shows a typical laptop computer similar to thePsion® Organiser(™). Again, the screen is in two parts and is foldableas with the mobile phone of FIG. 14a.

[0075] Although the foregoing description has focussed upon smallerscale screens, and in particular liquid crystal displays, it is to beunderstood that the invention is not so limited. For example, bistableor electroluminescent displays are equally susceptible to the use of amaterial, coating or structural formation that will allow bending oflight to minimize panel gaps between adjoining displays. Furthermore,the use of multiple television or video screens placed next to oneanother to form a giant display for large public areas such as shoppingmalls, is known. Typically, each video or television screen has adiagonal screen dimension of around 600 mm. Because of the additionalhardware necessary around the screen, there is usually a significant gapbetween adjacent screens. This can again be minimised using lenses toform a pseudo-continuous display. In this case, mage compression mightbe achieved electronically without moving pixels. Such an arrangementalso illustrates that the number of smaller screens that can be used tomake up the single, composite larger screen is essentially unlimited.

1. A visual display screen arrangement for displaying an image,comprising: image display means having a display area; a translucentcover member arranged to cover the display area and having a first covermember edge, the display area having an edge extending towards but notas far as the said first cover member edge; characterised in that thecover member has: (a) a generally planar portion covering at least apart of the display area and being arranged to pass rays of lightsubstantially without bending such that the majority of the display areaas viewed externally of the arrangement and through the said generallyplanar portion, appears substantially undistorted; and (b) a refractingportion which includes the said first cover member edge, the saidrefracting portion being arranged to bend only those rays of lightemanating from at or adjacent to he edge of the display area, such thatthe said display area as viewed externally of the arrangement andthrough the said refracting portion, appears to extend substantially asfar as the edge of the cover member.
 2. The arrangement of claim 1,further comprising: second image display means having a second displayarea; a second cover member arranged to cover the second display areaand having a second cover member edge located in use adjacent to thesaid first cover member edge, the second display area having an edgeextending towards but not as far as the said second cover member edge,the second image display means being arranged to provide a second imagewithin the second display area which is visible through at least a partof the said second cover member; the second cover member having: (a) asecond generally planar portion covering at least a part of the seconddisplay area and being arranged to pass rays of light substantiallywithout bending such that the majority of the second display area, asviewed externally of the arrangement and through the said secondgenerally planar portion, appears substantially undistorted; and (b) asecond refracting portion which includes the said second cover memberedge, the said second refracting portion being arranged to bend onlythose rays of light emanating from at or adjacent the edge of the seconddisplay area such that the said display area, as viewed externally ofthe arrangement and through the said second refracting portion, appearsto extend substantially as far as the edge of the second cover member.3. The arrangement of claim 2, further arranged to generate a part of animage both within the first display area and adjacent the first covermember edge, and also within the second display area and adjacent thesecond cover member edge.
 4. The arrangement of claim 1, claim 2 orclaim 3, in which the generally planar portion of the or each covermember is substantially coplanar with the refracting portion thereof,relative to the display area.
 5. The arrangement of any preceding claim,further arranged to display the said image such that it is compressedbut only in a region adjacent the or each cover member edge.
 6. Thearrangement of claim 5, in which the or each display area has aresolution adjacent to the respective cover member edge which is higherthan the resolution of the or each display area away from the respectivecover member edge so as to cause the said image compression adjacent thesaid cover member edge.
 7. The arrangement of claim 5 or claim 6, in.which the generally planar portion of the or each cover member iscoterminous with that part of the display area which is arranged todisplay an uncompressed part of the image, and wherein the or eachrefracting portion is coterminous with that part of the display areaadjacent to the respective cover member edge which is arranged todisplay the compressed part of the image.
 8. The arrangement of any oneof the preceding claims, in which the refracting portion of the or eachcover member edge is shaped so as to form a lens to bend light passingtherethrough.
 9. The arrangement of claim 8, in which the refractingportion of the or each cover member is formed into a convex radius atthe corresponding cover member edge so as to form the or each said lens.10. The arrangement of claim 8, in which the refracting portion of theor each cover member includes a region having a refractive indexdifferent to that of the material from which the rest of the covermember is formed.
 11. The arrangement of any preceding claim, in whichthe or each cover member is formed as a laminar construction.
 12. Thearrangement of claim 11, in which the or each cover member comprises alower layer adjacent the display area and formed of a first material, anupper layer formed of a second, different material, and apolarisation/compensation layer sandwiched between the upper and lowerlayers.
 13. The arrangement of claim 12, in which the lower layer isformed of glass and the upper layer is formed of a plastics material.14. The arrangement of claim 13, in which the refracting portion of theor each cover member is formed from the upper, plastics layer thereof.15. The arrangement of any preceding claim, in which the refractiveportion of the or each cover member edge includes a reflective orrefractive coating.
 16. The arrangement of claim 2, wherein the firstimage display means and the first cover member together form a firstscreen member and wherein the first cover member edge provides a firstjoining edge, and the second image display means and the second covermember together form a second screen member, and wherein the secondcover member edge provides a second joining edge, the first and secondscreen members being movable between a first position and a secondposition in which the first and second joining edges are adjacent, thefirst and second screen members are generally coplanar, and the firstdisplay area appears to a user substantially to abut the second displayarea at the confluence of the first and second joining edges.
 17. Thearrangement of claim 16, further comprising hinge means connecting thefirst and second screen members and constraining the first screen memberand second screen member to be foldable between the said first andsecond positions.
 18. The arrangement of claim 16 or claim 17, in whichthe first screen member and second screen member are each liquid crystaldisplays.
 19. A mobile telephone including the visual display screenarrangement of any one of the preceding claims.
 20. A digital computerincluding the visual display screen arrangement of any one of thepreceding claims.